The present application relates to an antiglare film, a method for manufacturing the antiglare film, a polarizer, and a display device. In particular, it relates to an antiglare film used for display surfaces of various display devices, e.g., a liquid crystal display (LCD), a plasma display panel (PDP), an electro luminescence (EL) display, a rear projection display, a rear projection display by using laser as a light source (laser TV), and a cathode ray tube (CRT) display.
Regarding various display devices, e.g., a liquid crystal display, a plasma display panel, and a CRT display, (1) a technology for reducing a reflectance by disposing an optical multilayer film or a low-refractive-index film on a display device surface and (2) a technology for diffuse-reflecting external light to blur a reflected image by disposing an antiglare film having a surface with fine unevenness have been previously adopted in order to prevent significant impairment of visibility due to reflection of external light, e.g., a fluorescent lamp, in surfaces.
The latter of the technologies described in the items (1) and (2) will be explained with reference to FIG. 7. An antiglare film 101 includes a base material 111 and an antiglare layer 112 disposed on the base material 111. The antiglare layer 112 contains fine particles 113, the fine particles protrude from the surface of the antiglare layer 112 and, thereby, a fine uneven shape is formed on the surface. The antiglare film 101 is formed by applying a paint containing fine particles 113, e.g., a silica filler and an organic filler, to a base material 111 and curing the paint. Regarding the antiglare film having the above-described configuration, the light incident on the antiglare layer 112 is diffused by the fine particles 113 protruded from the antiglare layer 112 and, thereby, the reflection due to surface reflection is reduced.
However, if the optical multilayer film is used, the production cost increases and, in addition, the antiglare property is not satisfactory. Even if the low-refractive-index film is used and the production cost is reduced, there is a problem in that the reflection is obtrusive because the reflectance is relatively high. On the other hand, regarding the technology for forming fine unevenness on a surface by mixing the silica filler or the organic filler and blurring a reflected image by diffuse reflection, since the shapes of protrusions formed by individual particles are steep, the antiglare property is obtained, but a feeling of white turbidity is intense. In particular, in the case where external light is intense, there is a problem in that the degree of contrast is reduced and the visibility is deteriorated.
Consequently, in recent years, a surface treatment in which the feeling of white turbidity is reduced (that is, the contrast is high) while the antiglare property is ensured has been desired. A few technologies therefor have been studied up to now.
For example, Japanese Unexamined Patent Application Publication No. 2005-316413 discloses an antiglare laminate produced by forming an uneven shape on the outermost surface of an antiglare layer in such a way that a plurality of aggregation portions having three-dimensional spatial structures formed from at least five fine particles are allowed to present in the antiglare layer and, in addition, the plurality of aggregation portions are prevented from gathering, in order to realize an excellent antiglare property, an improvement of contrast, an enhancement of transmission definition, a reduction in blurring of characters, and the like.
Japanese Unexamined Patent Application Publication No. 2006-54838 discloses an antiglare film which facilitates achievement of good resolution of displayed images of characters and the like and a state of clear contrast without a feeling of glare in the case where an image on a display surface is looked by controlling the haze, the glossiness, and the surface roughness.
Japanese Unexamined Patent Application Publication No. 2000-206317 discloses an antiglare film which allows the surface uneven shape to be minutely controlled at desired size and frequency of unevenness and has a periodical uneven shape, a polarizing film, a display device, and a method for manufacturing the antiglare film.
For the purpose of improving the feeling of white turbidity of the antiglare film, as shown in FIG. 8, it is conceived that the content of fine particles 113 in the antiglare layer 112 is decreased so as to increase the period of the fine uneven structure of the surface.
However, the two characteristics of the antiglare property and the reduction in feeling of White turbidity are in the relationship of trade-off. Therefore, it is difficult to design an antiglare film having these characteristics, which are mutually compatible, on the basis of the related art.
For example, if the uneven shape is formed from aggregation portions having three-dimensional spatial structures as in Japanese Unexamined Patent Application Publication No. 2005-316413, steep protrusions are formed on the surface. As a result, surface scattering increases and the feeling of white turbidity is enhanced.
Furthermore, it is difficult to obtain satisfactory antiglare property and contrast merely by controlling the haze, the glossiness, and the surface roughness as in Japanese Unexamined Patent Application Publication No. 2006-154838.
Although an appropriate antiglare property can be obtained by disposing the periodic uneven shape as in Japanese Unexamined Patent Application Publication No. 2000-206317, it is difficult to obtain satisfactory contrast. Moreover, a moire may occur because of the periodic shape.
If the antiglare property is restricted by increasing the period of the fine uneven structure of the surface as shown in FIG. 8, flat portions result between fine particles 113 protruded from the surface, as shown in FIG. 9, so that the antiglare property is reduced.
Accordingly, it is desirable to provide an antiglare film enable to the antiglare property and the reduction in feeling of white turbidity to become mutually compatible, a method for manufacturing the antiglare film, a polarizer, and a display device.